With development of vehicle technology, people's requirements in safety and comfort performance of vehicles has become higher and higher, and how to improve the safety and comfort performance of the vehicles has become one of the objects pursued by major vehicle manufacturers.
Three-point safety belts are common safety devices in vehicles. Nowadays, the safety belts in vehicles are basically three-point safety belts (sometimes the humble two-point safety belts are used in the rear row). The traditional three-point safety belt includes a winder, a belt body, a shoulder belt guide ring, a lock tongue and a buckle. The shoulder belt guide ring is fixed on the vehicle body, the lock tongue is sleeved on the belt body, and the buckle is fixed to one side of the seat. After the lock tongue is inserted into the buckle, the buckling point (i.e., a fixing point of the lock tongue and the buckle) substantially divides the belt body into a shoulder belt which restrains the chest of a passenger and a waist belt which restrains the abdomen of the passenger. An end of the shoulder belt which is remote from the lock tongue passes through the shoulder belt guide ring and is wound around the winder. An end of the waist belt which is remote from the lock tongue is fixed to the vehicle body by an anchor point (i.e., a fixing point of the vehicle body and the end of the waist belt which is remote from the lock tongue). When the lock tongue of the three-point safety belt is inserted into the buckle, the three-point safety belt has four fixing points which includes the anchor point, the buckling point, the D-ring point (i.e., a contact point of the shoulder belt and the shoulder belt guide ring) and the winder point (i.e., a connection point of the winder and the end of the waist belt which is remote from the lock tongue).
In order for convenience of wearing, the lock tongue is generally fixed to an upper portion (i.e., a position close to the shoulder belt guide ring) of the belt body through a lock tongue guide ring when the three-point safety belt is not worn. Therefore, when the lock tongue of the safety belt is pulled toward the buckle, the hand needs to be raised to a higher position to pull the belt body downwardly from top by the lock tongue. During the process of pulling the belt body by the lock tongue, the lock tongue will slide relative to the safety belt, which makes the lock tongue function as a movable pulley in a movable pulley system. However, pulling the movable pulley is a laborious process, and the fact that the belt body slides relative to the lock tongue increases the pulling resistance and energy consumption, which causes the process of wearing the safety belt to be a time-consuming, laborious and poor operation comfort process.
When the three-point safety belt is worn, the belt body of the winder first exerts a force on the shoulder belt, and then transfers the force to the waist belt through the lock tongue guide ring. Since the belt body of the safety belt has a greater friction at the lock tongue guide ring (especially when confronts collision), the effect on the waist belt will be delayed and weakened. When the vehicle confronts collision, the winder exerts a small preload and a low pre-tension speed on the belt body, which greatly affects the safety performance of the vehicle.
In addition, the anchor point (i.e., the fixing point of the vehicle body and the end of the waist belt which is remote from the lock tongue) of the current safety belt is fixed to the sill, which adds additional cost in design, manufacture and assembly.